We are given that "REASON" is encoded as "TDDQSK". Let's analyze the pattern used for encoding:
\[
\begin{array}{|c|c|}
\hline
\text{Letter} & \text{Code Letter}
\hline
R & T (\text{Shifted +2})
E & D (\text{Shifted -1})
A & D (\text{Shifted +3})
S & Q (\text{Shifted -2})
O & S (\text{Shifted +4})
N & K (\text{Shifted -3})
\hline
\end{array}
\]
The shifting pattern alternates: +2, -1, +3, -2, +4, -3.
Now, applying the same rule to "PRAYER":
\[
\begin{array}{|c|c|}
\hline
\text{Letter} & \text{Code Letter}
\hline
P & R (\text{Shifted +2})
R & Q (\text{Shifted -1})
A & D (\text{Shifted +3})
Y & W (\text{Shifted -2})
E & I (\text{Shifted +4})
R & O (\text{Shifted -3})
\hline
\end{array}
\]
Thus, "PRAYER" is encoded as "RQDWIO", corresponding to option (b).